Application of Lubrizol's specialty polymers in advanced battery manufacturing

• Main Author: Thang, Ai Qin
• Other Authors: Alex Yan Qingyu
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Battery
• Online Access: https://hdl.handle.net/10356/180872
• Institution: Nanyang Technological University

This thesis targets to apply Lubrizol’s specialty polymers in Lithium (Li) batteries. In particular, the application of Lubrizol’s acrylate-based materials to enhance battery cycle life. Three works were completed, and this thesis presented the compatibility of Lubrizol’s materials and the importance of interfacial engineering in both lithium metal batteries (LMB) and anode-free lithium metal batteries (AFLMB). Functionalized separator and gel polymer electrolytes were fabricated using specialty polymers from Lubrizol Southeast Asia Pte. Ltd. (LSAL) to achieve better cycle life in LMB and AFLMB. In the first work, a curated polymer blend from LSAL was first tested as a binder and dispersant of ceramic-coated separator in LMB. It was tested in LMB, i.e., a well-established battery system, instead of AFLMB is to limit the scope of study, focusing on just the mechanical and electrochemical performances of the polymer blend when tested in LMB. The polymer blend consisted of a (homopolymer) linear partially neutralized polyacrylic acid (PPAA) together with modified styrene maleic anhydride maleimide copolymer (PSMA). This work presented that the application of the polymer blend yielded an adhesion strength of ~151.4N/m with improved cycle stability, a capacity retention of 98.1% after 300 cycles at 1C at ambient temperature in LFP/Li metal cells. This blend also demonstrated enhanced cycle stability as compared to using PPAA and PSMA individually. Subsequently, a rigorous study on the modification of separator in AFLMB was carried out. This work is to investigate the effect of Li nucleation on bare lithiophobic Cu foil by functionalizing the separator with a cost-effective lithiophilic material. Amorphous antimony (Sb) was coated on a separator (SbSC) via magnetron sputtering. SbSC exhibits a large specific surface area which increases lithium (Li)-Sb alloy kinetic. This leads to an increase in Li wetting ability on bare copper current collector (Cu). When evaluated with LiNi0.8Mn0.1Co0.1O2 (NMC811) as cathode, the NMC811/SbSC/Cu cell exhibited low nucleation overpotential with dense, dendrite-free and uniform Li plating. It also demonstrated a notable lithium inventory retention rate (LIRR) of 99.8%, with high-capacity retention of 93.6% after 60 cycles at 0.5C-rate. This innovative method showcases a uniform Li-plating behavior, contributing to the extended cycle life of AFLMB. Lastly, a bi-layer gel polymer electrolyte (GPE) was fabricated to mitigate electrolyte leakages in AFLMB. In this work, the fabricated bi-layer GPE was made using LSAL polymer and was examined in AFLMB to understand how the polymers from LSAL enables a longer cycle life. In particular, the bi-layer GPE consisted of PSMA blended in partially neutralized acrylic latex [layer 1]/ Amorphous Sb [layer 2]). When the GPE was tested with Lithium Iron Phosphate (LFP) as cathode, the full (LFP/Cu) cell with this facile fabrication bi-layer gel electrolyte demonstrated a notable capacity retention of 91.6% after 110 cycles at 0.3C-rate. It also yielded a high lithium-ion transference number of 0.802. This work also shows that by partially neutralizing the acrylic latex, it showed a drastic expansion of its electrochemical stability window (ESW). This thesis shows that the selected acrylate-based polymers from LSAL are compatible in LMB and AFLMB systems. The mechanical and electrochemical aspects of polymers from LSAL were tested and investigated, then modified to enable a longer cycle life in AFLSSB.